Consider two developers that make 100k per year before taxes and live off of 40k / year. Now assuming they work for each other they pay 100k and get 65k after taxes, spend 40k and get to invest 15k which they spend on advertizing for their company.

Now assume the work for themselves They pay they only need to live off of 40k so they pay themselves 70k and get to invest 30k on advertizing without paying taxes on that value. Note: numbers are not accurate but they do give context. The idea, is companies can invest in future earns though things like advertizing or R&D without paying taxes on the income uses to pay for that advertizing.

Now you are supposed to pay yourselves market rate, but if you generate 300k in value each year you don't need to pay yourself that money.